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STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 The roles of stratospheric dynamics and chemistry for polar ozone anomalies in a 29 year assimilated ozone dataset Kiesewetter Gregor , Sinnhuber Björn-Martin , Burrows John Institute of Environmental Physics, University of Bremen We introduce a 29-year dataset of stratospheric ozone which has been created from sequential assimilation of Solar Backscatter UV (SBUV) satellite ozone profile observations into a chemistry transport model (CTM). Our assimilated dataset shows excellent agreement with ozone profile data from independent observations (satellite instruments and sondes), including during polar night when no SBUV observations are available. The dataset can thus be viewed as a consistent long-term dataset closing the gaps in satellite observations in order to investigate high-latitude ozone variability. We use the assimilated dataset to analyze the development and persistence of ozone anomalies in the Arctic stratosphere, and their relation to stratospheric dynamics and chemistry. Anomalies in the stratosperic circulation, expressed by the Northern Hemisphere Annular Mode (NAM) index, are shown to have a large influence on ozone anomalies. In particular, extreme phases of the NAM index (strong and weak vortex events) lead to the creation of distinctively shaped ozone anomalies, which first appear in the upper stratosphere and rapidly descend to the lower stratosphere, where they remain visible for up to five months. Using budget terms from the assimilation as well as regression analysis of CTM sensitivity runs, we further quantify the contributions of gas-phase chemistry, heterogeneous chemistry and dynamics to polar ozone anomalies, and their impact on mid-latitude ozone trends.
STP12 Abstracts Berlin, 12 - 16 July 2010 SCOSTEP Symposium 2010 Particle tracing within noctilucent clouds in the polar summer mesosphere Kiliani Johannes, Lübken Franz-Josef, Berger Uwe, Baumgarten Gerd, Hoffmann Peter Leibniz-Institute of Atmospheric Physics We use the LIMA/ICE Lagrangian model for NLC simulation to investigate the history of large mesospheric ice particles prior to and after observation and to look into the origin and development of noctilucent clouds. To that end, we scan given NLC events for large particles (e.g., > 20nm) and then trace those backward in time to their nucleation and forward to their evaporation. From this, characteristic properties like mean radius, growth rate, local water vapor (super-)saturation etc. are plotted in time series to characterize NLC particle development. As validation for the trajectory modeling, modeled winds from LIMA are compared to measurements of radar data from Andenes (69°N) and Juliusruh (55°N). We observe a generally good agreement of modeled winds with radar winds for the Andenes latitude, so the focus of trajectory tracing are NLC oberserved near 69°N. Higher and lower latitudes are also considered, but those results are used more cautiously, as validation for the winds used in modeling is not as conclusive in this case. Particle lifetime is dependent on latitude, with NLC particles observed near the pole remaining small and close to the mesopause much longer than those at lower latitudes. At 69°N, the typical growth and sedimentation process may take a day or longer, while ice particles observed at the very edge of the NLC latitude range tend to grow within hours before being observed. This may be explained with much more variability in saturation ratios of air carrying ice particles in mid-latitudes compared to higher latitudes. With few exceptions, ice particles growing to visible size evaporate within ~6h of observation, since they sediment to warmer regions and evaporate quickly once there. Thus, ice particle lifetime is almost entirely determined by the time the NLC particles take to grow to visible size.
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scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

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